Lithium ion secondary batteries can achieve a high energy density, and thus attract attention as power sources for cellular phones, notebook computers, and the like. Recently, lithium ion secondary batteries have enhanced output characteristics and enhanced long-term reliability such as storage characteristics, and thus also attract attention as power sources for driving the motors of hybrid vehicles (HEVs) and the like. In these applications, it is desired to achieve a higher energy density. In order to enhance the energy density, it is necessary to increase the operating voltage of the lithium ion secondary battery, and a non-aqueous electrolytic solution is desired that does not undergo oxidative degradation even at a high electric potential. For example, the use of an oxidation-resistant solvent or an oxidation-resistance improving additive, a surface treatment of a positive electrode, and the like can be considered as methods for enhancing the oxidation resistance of a non-aqueous electrolytic solution. Also, forming a film on electrodes such as a positive electrode and a negative electrode is a known method for suppressing the oxidative degradation of the non-aqueous electrolytic solution.
For example, Non Patent Literature 1 discloses a technique for adding thiophene to a non-aqueous electrolytic solution. Thiophene is described as forming a film through oxidative polymerization on a positive electrode and being capable of suppressing the degradation of a solvent with the film. Non Patent Literature 2 discloses a technique for suppressing the reaction of a non-aqueous electrolytic solution by inactivating a positive electrode with a phosphorous acid ester. Non Patent Literature 3 discloses a technique for forming a film on a positive electrode with benzene derivatives. Also, Non Patent Literature 4 discloses a technique for forming a film with a phosphoric acid ester.